1. Field of the Invention
The present invention relates to a lens drive control apparatus for a zoom lens system incorporating a switching lens group as disclosed in U.S. patent application Ser. No. 09/534,307 (Japanese Patent Application No. Hei 11-79572) filed by the same applicant of the present invention.
2. Description of the Related Art
To provide a zoom lens system having a high zoom ratio and at the same time to provide a miniaturized zoom lens system are contradictory demands. For example, although a small two-group zoom lens system can be relatively easily provided, when the zoom path (solution of loci) of lens group elements are obtained so that the zoom ratio can at a maximum, a collision would occur of lens groups at the telephoto position, or a collision of the lens groups with the image plane. When a three-group zoom lens system is used, it is possible to obtain a larger zoom ratio than that of the two-group lens system, however, providing a small three-group zoom lens system is relatively difficult. Furthermore, when the zoom power of lens group elements is determined in order to obtain an even higher zoom ratio, the accuracy of focusing is deteriorated due to mechanical limitations.
In order to satisfy the above mentioned demands, the applicant has invented a novel miniaturized zoom lens system having a high zoom ratio (U.S. patent application Ser. No. 09/534,307; Japanese Patent Application No. Hei 11-79572).
The characteristics of this zoom lens system are as follows: the zoom lens system includes a plurality of movable variable lens groups for varying focal length, at least one of the variable lens groups having two sub lens groups; one of the sub lens groups is a switching lens group serving as a movable sub lens group selectively moving against another sub lens group to be positioned at any of moving extremities in the optical direction, wherein the movement extremities of the movable sub lens group in the switching lens group are opposite to and away from each other at which the movable sub lens group can be positioned according to the selection of zooming zones between a short focal length zooming zone from a shortest focal length position to an intermediate focal length position(s) (there can be a single intermediate focal length position, or two or more intermediate focal length positions), and the other zooming zone (a long focal length zooming zone) from the intermediate focal length position(s) to a longest focal length position; and the fundamental zoom path of the switching lens group and the other variable lens groups are discontinuously determined at the intermediate position so that the focusing on a predetermined image plane may be performed according to the position of the movable sub lens group.